1. Technical Field
The invention is related to producing High Dynamic Range (HDR) video, and more particularly to a system and process for generating HDR video from a video image sequence captured while varying the exposure of each frame.
2. Background Art
The real world has a lot more brightness variation than can be captured by the sensors available in most cameras today. The radiance of a single scene may contain four orders of magnitude in brightness—from shadows to fully lit regions. Typical CCD or CMOS sensors only capture about 256-1024 brightness levels.
This limited dynamic range problem has inspired many solutions in recent years. One method of capturing the full radiance of a static scene is to take multiple exposures of the scene and then to combine them to create a High Dynamic Range (HDR) map [3, 7, 10]. The static scene requirement can be eliminated using multiple image detectors, novel sensors or spatially varying pixel exposures [8]. Mann et al. [6] register differently exposed frames using homographies, which allows them to estimate the camera response function and hence produce an HDR image from a panning video. Bogoni [1] extends the dynamic range of monochrome and color images by registering globally (using affine parameters) and then locally. However, details of the registration step and its robustness were not given.
Once an HDR image is computed, it must then be rendered to a display. Since typical displays are only able to yield about two orders of magnitude in brightness values, a contrast reduction must be performed on the HDR image. This so called tone mapping problem has recently been explored by a number of researchers [2, 4, 9].
However, none of these previous image-based methods is designed to efficiently create HDR video. Typical video footage captured using an off-the-shelf camcorder suffers from limited dynamic range. In addition, the prior methods would not allow a conventional video camera to be used to create HDR video. The present HDR video generation system and process remedies this problem.
It is noted that in the preceding paragraphs, as well as in the remainder of this specification, the description refers to various individual publications identified by a numeric designator contained within a pair of brackets. For example, such a reference may be identified by reciting, “reference [1]” or simply “[1]”. Multiple references will be identified by a pair of brackets containing more than one designator, for example, [2, 3]. A listing of references including the publications corresponding to each designator can be found at the end of the Detailed Description section.